The Value of Lung Scans

Three years ago, a landmark federal study found that testing many older smokers and former smokers with special low-dose CT scans substantially reduces deaths from lung cancer. Then, last year, on the basis of this and other research, the American Cancer Society and American Lung Association endorsed such screening.

Now the U.S. Preventive Services Task Force, an independent expert body that advises the government, has issued draft recommendations supporting annual screening. This means that Medicare and private insurers will cover lung cancer tests, and that they are likely to become as mainstream as mammograms and colonoscopies.

The Task Force advises that screening be offered to people who meet the criteria used in the landmark study—that is, current smokers or those who quit in the past 15 years, ages 55 to 79, with at least 30 "pack-years" of smoking. This would include, for instance, those who smoke an average of one pack a day for 30 years or two packs a day for 15 years. Because younger people and lighter smokers are at lower risk for lung cancer, screening is not recommended for them.

Lung cancer kills 160,000 Americans a year, accounting for nearly one-third of all cancer deaths and more than breast, prostate and colon cancer combined. This screening protocol, which would include 7 million to 10 million people, could save 20,000 lives a year, the Task Force estimated.

Lung scans: why not test everyone?

Like other cancer screening tests, this one has downsides:

It often produces false-positive results—false alarms that lead to further testing and sometimes lung biopsies, as well as fear and anxiety.

Even when the scans do detect cancer early, it may be very slow-growing and would never become life-threatening. This leads to what's called overdiagnosis and overtreatment. That is, people undergo repeated follow-up testing and often aggressive treatment, even though the cancer would never have killed them.

The special CT scans use relatively low levels of radiation, but done annually, the cumulative exposure will add up. Plus, the follow-up diagnostic scans to investigate detected lesions produce higher doses of radiation. The cumulative exposure will cause an unknown number of cancers 10 to 20 years later.

The net benefit of screening depends on how accurately the scans are interpreted and whether false-positives can be resolved without invasive procedures. Thus the test should be done only in medical centers with specialized radiologists and teams of experts.

For older people with serious health problems, the harms are more likely to outweigh the potential benefits. This is especially true if they are not healthy enough to tolerate treatment for lung cancer if it is found.

Bottom line: If you are 55 to 79 years old and have smoked heavily for many years, discuss the pros and cons of lung cancer screening with your health care provider.